The present invention relates to an oscillating signal generator utilized in a phase-locked loop and method for controlling the oscillating signal generator, and more particularly to a mechanism to compensate frequency variation of an oscillating circuit due to the temperature variation, and method thereof.
In a voltage-controlled oscillator (VCO), such as an LC (Inductor-capacitor)-tank VCO, the oscillation frequency of the oscillating output signal is very sensitive to the temperature. More specifically, each temperature-sensitive element in the VCO may react differently with respect to the temperature. Some elements may have positive temperature coefficients and some may be negative. Furthermore, the temperature-sensitive elements may be process dependent. Therefore, providing a temperature compensation method to model and compensate the oscillation frequency of the VCO with respect to the temperature can be a very difficult job, especially in a high frequency system. Moreover, in some continuous receiving or transmitting systems, the phase-locked loop (PLL) must continuously lock a predetermined input clock during the operation mode, thus it is difficult to calibrate the variation of the oscillation frequency of the VCO under the operation mode since it might cause the PLL fails to lock the predetermined input clock. Therefore, providing an innovated method to compensate the frequency variation of the VCO due to the temperature is a significant concern in this field.